Telephone-exchange system.



5.13. CLEMENT. TELEPHONE EXCHANG'E'SYSTEM. APPLECATIDRHLED IULY 2, 1932. I

Patente Jan. 52,1917.

E. E. CLEMENT.

ImPHoNE EXCHANGE SYSTEM.

APPUGAUON FILED HJLYIZ, 1912- r Patented Jan. 2,1912,

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TELEPHONE EXCHANGE SYSTEM.

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TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED JULYIZ, 1912.v

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TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED JULY [2. $9l2- Patented Jan. 2,1917.

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TELEPHONE EXCHANGE SYSTEM.

APPLICATION HLED JULYIZ. {912.

Patented Jan. 2,- 1917.

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BEST AVAILABLE COP UNITED STATES PATENT OFFICE.

EDWARD E. CLEMENT, OF WASHINGTON, DISTRICT OF COLUMBIA, ASSIGNOB, BY MESNE I ASSIGNMENTS. TO JAMES R. GARFIELD, TRUSTEE; 0F CLEVELAND, OHIO;

Application filed July 12. 1912. Serial No. 709,097.

lie it known that l. Enwwuu E. (u-:iucx'r. a citizen of the United States. residing at \Yashiugton. in the District of Columbia. have invented certain new and useful improvements iu 'lelephoue Exchauge Systems. of which the following is a specification. reli rence being bad therein to the acconunurving drawing.

My invention pertains to telephone exchange systems and is especially applicable to automatic and semi-automatic connective systems therefor.

.\.u object of my invention is to provide a novel arrangement of circuits and apparatu \vhcreb subscribers lines are intercouuected by means of power driven switches instead of the usual impulse driven switches, thereby doing away with the necessity of an impulse sending machine.

Another object is to provide a novelmethod of control for power driven switches whereby they may v ubserve the functions of so-called selector and connector switches.

further object of my invention is to provide a unidirectional power driven switch of novel construction for interconuectiug subscribers line circuits with controlling means therefor separate from the driving means. and to so construct such a switch that it may be used either as :1 noranally active or inactive switch and can be r *adily changed from one type to the other.

Other objects and advantages will be iuafter set forth in detail.

Generally stated. the invention conu'n'ises a telephone exchange system in which the line. circuits are intert onnected by means of power driven switches} and a novel method of controlling the "mo-ve'mentst. of said switches by means of impulses sent from the switches to the controlling means. whereby the usev of a sending machine is obviated.

My invention'is illustrated in 'the accompanying drawings in which:

l igures 1. 2 and 3 are respectively front. side and top plan views of a power driven switch comprising a group of ten switching elements. Figs. 4 and 5 are detail views of one of the switching elements. Fig. (3 shows subscribersline circuits terminating in contacts of power driven primary selector switches. Fig. 7 is a powerdriveu first herelector switch audits associated trunk and circuits. Fig.8 is a power driven connector Specification of Letters Patent.

TELEPHONE-EXCHANGE SYSTEM.

Patented Jan. 2, 1917.

switch and its associated trunk and circuits. Fig. 9 is a power driven secondary selector and associated circuit. Fig. 10 is a diagram of the apparatus and circuits constituting the switch controlling device. Fig. 11 is a four party line circuit and terminal appa-,

bank 500 containing pairs of contacts such as 501, 502 and 503 arrangedin vertical groups (Figs. 4 and 5), and the groups ar ranged in an are so as to be successively engaged by the wipers 504. The wipers 504;

are bridging wipers, adapted to bridge'or form a shunt across each of the pairs of contacts of'a group. There are twogroups of bridging wipers 504 set 180 degrees apart. They are rotated by a common. constantly rotating shaft 540. and their movements controlled by a clutch member 505 operated upon by an electromagntt 506. The contact banks 500 are secured to standards 507 and 508 by means of the. binding plates 510 and nuts 511. and to the rear standard 509 by means of a bracket. 512 and nuts 513. The end of the bracket 512 is preferably forked to facilitate assembling and the ends of the binding plates 510 may also be forked for the same reason. The standards 507, 508 and 509 are rigidly secured at top and bottom in triangular castings 514 and 515 and extend through the lower casting snfliciently t0 aflord attachment of a third casting 516. A rota-table shaft 540 is mounted .in bearings 517. 518 and 519 in the castings (see Fig. 1), the lower bearing 519 being preferably a thrust, ball bearing. The shaft 540 is adapted to be driven by power transmitted from a counter-shaft 520 through the usual bevel gears and a worm gear 521- Arranged at intervals along the shaft a re clutch collars 523. one for each switching elemenhrigidly fixed to the shaft by means of set screws or the like. A split lillb52l: carrying the wiper arm 525, fits loosely on gether.

BEST AVAILABLE COP the shaft and hours upon the upper surface of the clutch collar. At either side of the hub are clutching pawls 505 pivoted at their upper ends to the hub and adapted to fall into av notch 526 in the clutch collar The pawls 505 extend downwardly beyond the clutch collar and are bent outward at an angle as shown in the lower switching element in Fig. 2. Below the clutch collar is an annular platform or rim 541 formed with a sleeve 52? fitting loosely on the shaft 540 and hearing on the upper surface of an abutment ring 5:28 fixed rigidly to the shaft. The periphery of the rim 541 is rounded or beveled and the upper surface of the rim is provided with a brake pad of leather or the like. The rim 541 is adapted to reciprocate rcrticallyon the shaft 540. between the abutment ring 528 and the clutch collar .323. by the energization and deenergization of an clectromagnet 306. Motion is transmitted to the rim 541 from the armature 543, of the magnet by means of the armature lever 542-, and the armature and lere are restored to normal position as shown by retractile springs 544. Each clutch magnet 506 is held firmly in its place on the switch by a cast yoke 529 upon which it is rigidly mounted by means of screws 530, the yoke being clamped at each end to the standards 507 and 508 by means of forked clamps 531 and setiscrews The split hub 52% is formed with flanges 535 and 536 spaced apart to receive between them the wiper arm 525 which is recessed in the center, so that it can slide between said flanges and straddle the hub. One half of the split huh has a flat key-way 530 milled in the flanges to receive a key 537 which passes through notches 538 in the sides of the recess in the wipearm. said hey being held in place by a set screw 545 threaded in the key and bearing against the huh. The wiper arm 552-) and the. key 537 thus hold the huh to- When the switch is used as a coin stai'it-ly rotating vprimary or secondary le ior. the clutch magnet is arranged as shown. namely. to allow the clutch members to normally engage and to disengage them and stop the wiper arm upon energization. Also, when used as a constantly rotating switch; the contacts and wipers are so arranged that as soon as one set of wipers passes oil" the last group of contacts the other set will engage the first group, as shown in Fig. i.

When the switch is used as a normally inactive switch such as a selector or connector,

ii necessary that it have a normal or Zero position and so in such cases the contacts are arranged so that when the wiper arm 52."; i in the position shown in Fig. l'the wipers will be clear of all contacts. used as a seleetor or connector it is necessary to proifide 'ayset of oil normal contact Also whensprings. as shown at 533 in Fig. 4, consisting of a bank of contact springs mounted on the yoke 52!) and adapted to he actuated by either one of the studs 52H carried by the wiper arm 525. it is further to he noted that when used as a normally inactive switch. the clutch magnet is arranged so as to allow the clutch members to remain normally out of engagement and to cause them to engage upon energization, as shown in diagram in Fig. 7.

All the switches may be equipped with a bank of oii"-noi'i1uil contact springs 53 and studs 534, so that the only alteration neces sary in changing from a cont-imlously actuated switch to a normally inactive switch would he to wire the, (id-normal springs and reverse the operation of the clutch magnet. in mounting the moving parts of the several switching elements, the clutch collars 523 are set on the shaft with the notches 5% of the different collars arranged at different angles so that when their associated wiper arms are in motion they will he spaced apart atv corresponding angles as shown in Fig. 3 thus preventing any 'two sets of wipers from engaging the same multiples at the same time. With this arrangement wiring is facilitated inasmuch as the contacts of a group of switching elements may he multiplcd verticall y instead of staggering.

It will be seen from the foregoing. that any one or more of the switching units may be assembled or taken apart without disturbing the other units.

In Fig. 6 three substations are shown whose line. wires 1 and 2 terminate in the.

central office in contacts of a cut-oil relay ll contacts of said relay to the battery B through a line relay ll. The line wires 1 and 2 of each line are adapted to be connected through front contacts of the cut-oil relay l to extensions 3 and 4 respectively, terminating in multiple contacts in the. banks of primary selector switches such as S. The line relay ll. is adapted when energized to connect ground to its associated multiple test contacts 549 in the primary selectors such as S. The primary selectors are provided with clutch magnets such as M which normally allow the wipers to ro tate and upon energization operate to disengage. the clutch members and bring the wipers to rest. The contacts 549, 551 and are normally open and-when bridged or shunted by their respective wipers 550, 552 and E54 connect the extensions 34 and the test circuit 559 to the conductors 5. 6 and 557 respectively.

In Fig. 7, the trunk conductors 5 and (i extend from the primary selector switch S by way of conductors 595 and 597 respectively through normally open contacts of a control relav R to tip and sleeve battery nd are normally connected through back the clutch magnet M (Fig. 3) and both are energized over a common circuit including the wire 558, normally closed contacts of relays R and R and wire 557 leading to the test contacts of S (Fig. 6). Trunk cut-off relay It is partially controlled through a front contact on R and partly over a wire 107 leading to the'operatofs circuit; Relays'R and R are release relays for the prin'iary selector switch S and firstselector respectively. The first selector switch S? is'the same as 5 except that it has four sets of contacts in its banks and. is adapted to assume a normal or zero position as shown in the drawing and to be rotated upon the actuation of its clutch magnet M. ()ti-normal springs 567. 568 and 569 connect one terminal of relay R toground through wire 570 when the switch S is at normal; and when the switch is off-normal, they open the first connection and connect ground to the'release relays R and R by way of a hack contact on tip relay R and wire 571. Relay R is initially energized through a front contact of relay R and off-normal spring contacts 568569, and locks itself to ground through a frontcontact wire 147 and a back contact of relay R byway of conductor 593. Lamp L is an oft-nornnil signal lamp and is oflUSGd to glow as long as the switch S is out of its normal position, its circuit being completed to ground through contact springs 5(i7568. Relays R and R are the switch control relays and directly control the clutch magnet M In the contact bank of switch S, the ppper row of contacts 572 have their upper member connected in multiple to wire 573 connecting with one terminal of relay R and their lower members connected to battery through battery lead 574. Conductors 573and 574 are bridged by a resistance F. The contacts 572:116 so spaced apart that as the. bridging wiper 575 passes from one contact to the succeeding contact the shunt around resistance '1' through the contacts is momentarily removed. In the second row 0? contacts. the lower members are connected in multiple to wire 147 while the upper "members constitute multiple terminals of difi'erent test wires such as 200 leadingto connector switches.

In the third and fourth rows ofcontacts 5(i1 and 560, the lower members of the retrunk conductors land 10 while the upper members constitute multiple terminals of different connector trunks such as 15 and 16.

Referring to Fig. 8 the connector switch S is the same in structure and operation as except that the off-normal contact springs are more numerous and the test contacts are omitted. The first row of contacts is connected to form ten groups of ten, the first contacts 577 of all the groups having their upper and lower members connected in multiple to the conductors 580 and 581, respectively while the remaining contacts 577.of all the groups have their upper and lower members connected in multiple to the conductors 580 and 581 respectively, the conductor 5S1 'leading to a front contact on the relay R tween the conductors 580-581. The bridging wipers 582, in passing over the contacts 577 and 577, alternately close and open the shunt around the resistance in the same manner as that of S. The contact rows 578 and 57$) have their lower members connected in multiple to the trunk conductors 18 -and 17 respectively. while their upper members constitute multiple terminals of different substationlines such as 255 and 254, respectively. T'runk condi'lctors l7-1S are connected through front contacts on relay R to conductors 15-16 which terminate in A resistance 1' is bridged be-,,

multiple contacts 560-561, (Fig. 7) of different first selector switches such as Relays ]i and I supply current to the called line through their windings. R also controls the release circuit nd R are-,- as a trunk cut-oil relay. 1 and 1" are the switch control relays reciprocally controlling and controlled by the switch H1. H

'swers or until the calling party hangs up his receiver.

111 case the called party is busy, relay It will be decnergized by action of test relay R Relays R, R and R all have their circuits completed to the grounded side of battery through lest wire. 200, contacts 576, conductor 147, 593, and back contact of relay R to ground.' '7

Relay R is adapted to normally connect the conductors 58()-581 to conductors 58358-l respectively and iipon cnergization, to open this connection and connect conductors 5R()581 to conductors 585-58G respectively, and also to connect conductor 581 to conductor 585. The energization of It also removes a shunt fromv conductors 58558(i at 1'', and completes the energizing circuit of R at normally opcnicohtact ,r,7a

'also controls the switch S by means of a Relay 1c is a self locking relay and its function is to open the controlling circuit 340 between relay It and clutch magnet M upon the secondary movement of the connector switch :5.

The switch S restores by continuing its motion until the wiper Q0870) disengages the contacts 8700 and assumes the normal or Zero position as shown. The wiper we just before reaching normal position connects the free side of battery to the release relay R by way of contact Us and conductor 269. The switch 8 continues to rotate to its normal position after the called party hangs up his receiver. thus providing a slow release after connection.

Relay R is a ringing relay adapted to be intermittently energized thri'lugh an interrupter I. B is a busy back circuit which is connected to one side of the calling line whenever the called line tests busy.

In Fig. 5) is shown a power driven secondary selector switch S which is identical in its operation to the primary elector switch S (Fig. (3). The switch S (Fig. 9) has four rows of contacts in its bank. The test contacts 58] have their upper members connected in multiple to one terminal of relay R and their lower members connected each through a conductor such as to to a front contact on the control relay of a primary selector (Fig. 7). In the row of contacts 588 (Fig. 9) the upper members are connected in multiple to conductor 109 and the lower members are connected separately to wires such as 107 leading to the trunk cutoft relays such as R o'l Fig. 7. in the row 589 the upper members are connected in multiple to the tip conductor 131 of the. operators control circuit and the lower memhers are connected separately to the tip control wires such as 130 leading to the first selector circuit. In the row 590 the lower members are connected in niultipleto the sleeve conductor 132 and the upper members are connected separately to sleeve control wires such as 135 leading to the. first selector switches. Relay R is a control relay energized when the switch S engages the con tacts associated with a. calling primary selector and actuates to close the circuitof the clutch magnet M, and to partly close the circuit of listening relay W. The calling relay R is also energized when the switch S engages the contacts associated witha calling primary selector and actuates the calling signals such as N. the calling lamp L (Fig. 10) and the meter Listening relay It operates to connect the operators listening set OR across the trunk 153L439 in the usual manner. It is the starting relay and is energized in series with R (Fig. 7) by the closure of key SK (Fig. 10). The actuation of R completes the circuit of the stepping magnet M and closes the circuit of guard lamp L (Fig. 10) and disconnects battery from the first five contacts in the lower bank of switch S. 5 is the oper ators control switch stepped around by the magnet M and operates to distribute the circuit connections between the operators control circuit (Fig. 9) and a switch control circuit (Fig. 10). The switch S is restored in a manner similar to that of the switch S by a circuit closed. through the magnet M and interrupter I upon the actuation of relay It. Just before the switch S reaches its normal position a cam on the spindle operates to momentarily close the contacts NSF-168 which completes the circuit of release relay R. of the switch S. Relay R is the trunk starting relay and is also used for release in case the calling subscriber has hung up his receiver or if the operator fails to get a response on operating the listening key. it controls the connection of a tone test signal to theoperators listening circuit.

Referring to Fig. 10, number one key of each strip is connected to the first contact I on the impulse receiver S which takes one step at each impulse sent back from the switches; number two key to the second contact (Z and so on to number ten key which is connected to the tenth contact (1 Each strip of keys has a common wire connected to one contact of each key in the strip and leading to its proper contact in one or the'other ofthe controlling banks associated with switch S The order in which these are arranged to transmit impulses in proper sequence is as follows: Atthe first rotation of the impulse receiver the first strip of keys K (hundreds) is connected to the tip side of the trunk; second rotation, ten testimpulses to impulse receiver over sleeve side of trunk: third rotation. selective ringing strip K connected to tip side of trunk; fourth rotation, keys K (tens) connected to sleeve side; fiftlrrotation, keys K (units) connected to tip side of trunk; during the fifth rotation and just after the units impulses have been sent, a single test impulse is sent to sleeve side of trunk; after the fifth rotation, arm 'zcs engages contacts connected to battery energizing relay E. This relay unlocks R restores switches S and S thus disconnecting secondary switch S from the primary trunk.

In Fig. 11 is shown a four party line to which are connected the substations A A, etc. and which terminates in the central oliice in contacts of the cut-oii' relay R through which it is normally connected to theusuallinerelay. Theextensions254-255 terminate in multiple contacts of connector switches such as S (Fig. 8).

Figs. 12, 13 and 14: are similar to Figs; 6, 7, 8 and 9 except that the primary and secondary selection is accomplished by the use 15 I of two-motion step by step switches instead of the single motion power driven switch. Figs. 12, 13 and ll are to be substituted for Figs. 6; 7, 8 and 9 to show a complete conr mercial embodiment of .iny invention.

Referring to Fig. 12, each line circuit 1-2 is provided with a line relay R and a cutoff relay R which when energized disconnects the line relay R and connects the tip and sleeve sides of the line to its multiple bank contacts in the primary and connector switches of its group. The attraction of the armature r of the relay R connects ground to the individual test contacts of the primary switches S". The attraction of armature r locks the Lrelay R on short circuit to ground through armature r of relay R, which prevents interference by the subscriber'in case he should move his receiver hook. The line relays R'are divided into groups of ten and the windings of each group are connected in multiple to the winding of a relay R common to the group, which when energized connects ground to the row contact of the primary switch through the armature 7', thus designating the group of lines calling, while the relay R designates the particular line in the group. Associated witheach primary distributing switch 3 there is a secondary distributing switch S and a kick-off switch S. The function of the secondary distributing switch is to pick out an idle operators circuit and start the same to testing for the group of primary trunks over which the call originates. This can be done because there being only one switch 5 for each group of one hundred lines, that is to say for each group of ten trunks such as shown n Fig. 13, and since it is convenient to arrange the contacts of each group of ten trunks in one and the same row in the secondary selector switches S" (Fig. 14'), each secondary distributing switch can therefore be directly identified with its own associated row of primarytrunk contacts in each of the secondary selector switches.

Referring to Fig. 13, the relay'R the row test relay, and is energized when the wiper 'uf finds an active contact. disconnects rotary relay 1 and in its place connects vertical relay R The relay li is used in testing for the individual contact as well as a battery supply relay for the calling subscril-ier. When energized this relay disconnects the row relay R". of relay' R disconnects the relay li' from the test wiper 10 and connects it to the sleeve wiper w" in series with the cut-off relay R RelawlP is the tip battery supply relay and controls the release magnets M and it after the first selector switch S has moved off normal. The relay R is used for opening the talking circuit while the impulses are being sent to operate the outgoing The dcenergizing' switches. This relay also with R jointly controls the relay R Relay R is the test relay having its locking contact 1'' connected to the test wire 14?. Its circuit is initially closed through a front contact of relay R Referring to Fig. ll relay It is the row test relay and R the individual test relay. Relay 1 32 is the control relay and corresponds to relay B (Fig. 18). Relay R is the signal relay and pulls up in series with relay B (Fig. 13) after the primary trunk has found the line and the secondary switch S has found the trunk.

The operation otthe system shown in Figs. (3, 7, 8, 9 and 10 is as follows: Subscriber at substation A upon lifting his receiver closes his line circuit energizing the line relay R by current from lmttery 15 through It, back contact of cut-olf relay R line wire 1 through circuits ol substation A back over line wire :2 and to ground by way of back contact of the cut-off rclay. Relay R upon actuation connects the ill upon actuation disengagcs the clutch members of switch i) causing the switch to come to rest with its wipers 550, .352 and 554 in engagement with the contacts 5&9, 551 and 553 respectively. The closure of contacts and :5 connects the extcnsions ll-lwith-the trunk 5 o. Relay R upon actuation connects battery to wire 45 and connects one terminal each. ol tip and sleeve relays it and li to the tip and sleeve trunk conductors 5 and i by way of wires 59 l5$l5 and rmrwmu. bcctivcly. (urrent now flows from battery B (Fig. 7) through R. 596. contact ol It. 597. sleeve conductor (3 into Fig. (3, 553. r, lt' to ground. energizing relays It and R. R upon actuation completes the circuit of tip relay R in series with R and the line circuit. which circuit may be traced as follows: battery B (Fig. 7) through R lo extension 4 (Fig. (i), as above traced, and thence through lower armature of it. lino wire '2. substation A, line wire 1. upper armature of R extension 3, contact 551, tip conductor-5into Fig. 7. 595, contact oi R 594 to ground through R. The actuation of relay li (Fig. 7) connects battery to wire 591 direct and opens the contact between 591 and 557 thus connecting the clutch magnet M and control relay R to battery by way of wire .158, normally closed contact of R 591 and armature of R to battery B, as long minal of the trunk cut-off relay It. Switch 5 (Fig. 9) in rotating brings its wipers into engagement with contacts 587, 588. 589 and 590, whereupon the closure of contacts 587 completes the energizing circuit of control relay R over the following path: B, (Fig. 7), through front contact of It, 45, into Fig. .1, contact 587, 597, it, 75, through springs 71-T3 of operators jack J to ground. Relay 11* upon actuation closes the circuit of clutch magnet M to battery and completes the circuit of relays ll and It" (Fig. 7) in series from ground through grounded contact of it, 116, 1", 115. 1' 111, i 11:3, 11'. 11:, 111, 1. 1011, contact 588, 107, into Fig. 7. R, 108, (13, T to battery. The relay R becoming ener gized closes circuit of night alarm N through; B, 86, 110, 117, 118, 1, 1.15), N to ground; closes circuit of guard lamp if (Fig. 10) through B, (Fig. 9), S6, 110, 117, 118, 1' 120, 121, mm Fig. 10, L to ground; closes circuit of service meter E (Fig. 9) through B, armature 7' 122, 212 and magnet of service meter I) to ground; and a line lamp L (Fig. 10) through B (Fig. 9) T 122, 123, into Fig. 10, L to ground. The operator perceiving the signal, depresses listening key LK (Fig. 10) energizing listening relay B" (Fig. 9) through: B, contact of R 598, R1 125, into Fig. 10, contacts of key LK, 120 to ground. Relay R energizing, opens series circuit of relays R and R" at and locks itself to ground through 2- and 114 as previously traced. Relay R deenerdigit, that in the third strip. K

gizmg opens circuit of relay R at r Relay R also completes the operator's listening circuit as follows: receiver OR, .127, plug tip 7), spring j, 128, r 129, 131, contacts 589, 130,v into Fig. 7, normally closed contact .R, 133, 9, contact of R 7. condenser C 5 into Fig. 6, contact 551, through substation A and back by way of contact 553, 6, into Fig. 7, condenser C 8, contact of R, 10, 134, normally closed contact of R, 135 into Fig. '9, contact 590, 132, 136, r 137, induction coil IC,.138, jack spring 7', plug sleeve p, 139, to receiver OR.

The operator, on ascertaining the number wanted sets up the same on her key set, (Fig. 10), by depressing the key in strip K corresponding to the firstdigit, that in the strip K corresponding to the second.

CO1'X'Sp0n(.-

ing to the third digit, and that in the strip K corresponding to the particular ringing generator to 'be selected, and then aetnates starting key, SK, whereupon starting relay R (Fig. 9) is energized in series with trunk cut-ofi' relay R? (Fig. 7) through: ground, 126, (Fig. 10) key SK, 140, (140 Fig. 9) R 141, 111, 1' 109, 588, 107, (107 Fig. 7), R. 106, 63, 7' 234, battery to ground. Relay 11* opens trunk conductors $lT and 108 at r and r and Tenergizcs relay R through: B, 31, 41, r 112, R, 570, off-normal contacts 56$):'i68 of switch ti to ground. Armatures r and 1" connect the control wires and to control relays R and It, respectively, while armature r connects conductor 147 to one terniinal of relay Starting relay K (Fig. 9) takes ground oil relay R" through 114-, at 1' and locks itsell through 118. 2' and 115 to ground as previously traced. Armature r connects starting wire 151 to stepping magnet M" through: B, (Fig. 9) 86, 110, 117, MY, 152, r 152, 1' starting wire 15], (151 Fig. 10) contact 0 to ground; so that said mag,- net is momentarily energized, stepping switch S forward one step.

The first step of switch S" brings the wipers one, we and 208 into engagement i with the first contact 1& etc. of their respective hanks. \Viper arm we connects ground to the common wire 105 (Fig. 10), and relay R (Fig. 9') is energized by current from B, 86, '10s, 13, 401, 402, R to ground. The actuation, of R connects the tip conductor 131 to the con1- mon impulse conductor 403 at 2- which completes the circuit of relays R (Fig. 71 and R (Fig. 10) in series as follows: E (Fig. 7), 574, resistance 7' 573, R 1.7-1, contact of R, 130, into Fig. 9, contact 589, 1331, contact of R 403, into Fig. 10. R", 404, 1' to ground.

The windings of relays R and R are so adjusted that only the relay R will actuate in series with the resistance r, the relay R" remaining inactive until said resistance is shunted by closure of the contacts The actuation of relay R connects the wire 592 to ground thereby energizing clutch magnet M, which magnet? upon actuation operates to cause the clutch, members of the normally inactive switch S to engage which sets the switch to rotating. As soon as the switch moves out of its normal position contact is opened between springs 568-569 and closed tract its armature r? which closes the circuit of stepping m:1gnet M of switch S which steps its wipers around mto engagement with their respective first contacts. 1

B through contact 116. g;

of key strip K 1:

The opening of contact (i deenergizes the stepping magnet M of switch S. \Vhen the wipers 575 disengage the first multiples of contacts 572.the shunt is removed from other step, and so this cycle of operations is repeated until wiper c of switch S e11- gages the contact leading to the particular key depressed in the first key strip K, which in this case would be contact is then completed through relay R over the following path: B, R, 406, (l 4107, 108, A12, 105 into Fig. 9 to ground through wiper we of S The'actuation of It opens the series circuits of R and R at 2- closes the circuit of h through r to interrupter Land locks itself'to ground by way of contact +09, r 110, multiple contacts d" of S? to ground. R retracting its armature opens the circuit of clutch magnet M which deenergizing disengages the clutch members of S and the switch S comes to rest'with its wipers resting on the first set of a group of ten sets of contacts leading to the two hundreds group of connector trunks (Fig. 8). The switch SP continues to be stepped around by the intermittent energization of M through the interrupter I, until the wiper arms s 8 etc., assume the normal position as shown whereupon the locking circuit of R is opened between contacts '(Z and wiper s and R becoming deenergized opens the intermittent circuit of M at r \Viper s arriving at normal position closes wire 151 to ground through contact 1! again energizing stepping magnet M (Fig. 9), stepping the wipers of S intoengagement with the second set of contacts, in a manner as before described. Relay R is now energized through Wire 402 and'contact 2a and ground is connected through wiper wa to wire 411 leading to relay R of Fig. 10. Actuation of R connects the grounded side of battery to wire 403 through armature r and wire 412, and completes the circuit of R" through wire 4:06 and armature 1' to ground. R upon energizetion starts the switch S on another semirotation in a manner as before described. The actuation of It connects the sleeve trunk conductor 132 to wire 403, completing the following circuit: ground- (Fig. 10) through armature W" of R, 412. 103 into contact 590, 135

Fig. 9, contact of R 132, v into Fig. 7. front contact oi R, 199, R to battery. Actuation of It removes the ground connection of R through 576 deenergizing It it' the trunk 15-16 to which the first selector S 15 now connected is idle.

A circuit.

R retracting its wires 130-171 and 135-199 and connects 130-133 and 135-131, and the relay R is deenergized by the opening of circuit through wire 109. The momentary energization of R did not affect magnet M as the armature of R' 'was .depriwd of its ground connection, the switch S thus remaining connected with the first set of contacts ot' thetwo hundreds group. However, it' said trunk is busy, ground potential Will exist at the contact 570 and may be traced from thence through wire 147 to the locking armature of R, so that when the original energizing circuit through wire .370 is opened R will remain locked to ground through wire 1&7. M is energized by current from. battery through )1, 592, front contact of R .303 to ground by way of wire 147. The switch S thereupon continues to rotate until it engages a set of wipers lead ing to an idle trunk 15-16 of a connector switch (Fig. 8). whereupon the, ground connection through wire HT is opened at contact 570 thereby deenergizing clutch magnet M and relay R The deenergization of M causes switch S to come to rest with its contacts bridging the contacts 576, 561 and 560', the upper membersof which individually connect to conductors 15, 10 and 200 leading to an idle connector switch (Fig. 8). Relay R retracting its armatures connects the control wires 130 and 135 to the tip and sleeve conductors 9 and 10 through wires 133 and 134, respectively, in the same manner as before described.

Switch t (Fig. 10) through the operation of magnet M in circuit with interrupter I, and upon arriving -at normal position as indicated again deenergizes R and causes the switch S to take another step, this time bringing its wipers'into engagement with the third set of contacts. -.-\t his juncture relay R is energized through wiper aw and ground is connected through wiper 5108 to wire $30 leading to the key strip K". Actuation of R completes the circuit of relays R" (Fig. 10) and R (Fig. 8) in series as follows: Battery B (Fig. 8) through R, H4. armature ot R through 215, 21-1. M. 213, 212, to

battery through ott-nornnll contact springs AL-210. Actuation of M steps the wipers of S around one step. and at the end of its stroke opens the series circuit of relays continues stepping -tact of R. 583.1 15 into Fig. 7,

IR and R at m. it" deenergizing, deenergizes M and the deene'rgization of R opens the circuit of M at P M retract ing its armature at m again closes its circiut of R and R which results in a second energization of M and so this cycle of operation is repeated stepping the switches t5 and S around in synchronism until the wiper s of S engages the third contact (1, which opens the series circuit of relays it and R and sets the switch S to rotating to its normal position as above described. The latter circuit of R may be traced from B through R 406, (I 431, K", 430 into Fig. 9 to ground through wiper u-sf". The first energization of R3? (Fig. 8) energizes it by current from battery through r 2&7, It, 202. 200 into Fig. 7, contact 576. 147.

593 to ground through contact of It. 11, upon actuation, locks itself to battery through 2&9, 1' 250, and 1' The first energization of R also completes the circuit ct it as follows: E, T 930, it, 235. contact of R 236 to ground by way of wire 200. R, upon actuation, locks itself to battery through 232, 7 233 and r When the wipers of switch step onto their fourth contacts relay R is energized over Wire 4022" through wiper ms and ground is connected through wiper we to 447, leading to the second strip-of keys K. (Fig. 10). R upon actuation connects rclays R" and R in series with the resistance '2'? (Fig. 8) in a circuit which may he traced as follows: battery through armature r (Fig. 8), 9' 232, 230. 22s), 584. back contact of R, 581. 0' 580 back con- 7 contact 561, 10, 134, and so on through windirigs of relay Rf (Fig. 10) and armature 2" to ground, as previously traced. Relay R will not actuate in series with resistance 7' while the relay B does actuate, and in so doing, connects grouml through armature P 240 and 595 to clutch magnet M M thereupon energizes and actuates to engage clutch members of connector switch S which starts to rotate. As soon as S moves out of its normal position the circuit of magnet M is opened at elf-normal contacts 210-211, battery is connected to wire 264 through contacts 210-246 and the wire 595 leading from magnet M is connected. to wire 596 through contacts 237-238. The connection of battery to wire 264 partially completes the circuit of the shifting relay R by way of wire-597. As the switch S continues in its motion its wipers engage and bridge the contacts of the several rows. 577-477, 578 and 579. Each time a tens contact 577 is closed resistance 7' is shunted and the increase in current flow energizes relay R (Fig. 10) which results in the intermittent energization of said relay, and

the constant energization of relay R during the movement of switch S.

The switches S and S? continue to rotate, theswitch S stepping its wipers around one step each time one of the contacts 577 is closed by the wipers of switch S" so that the wipers of both switches will engage contacts of the same ordinal at the same time. When the wiper arm W" engages the fourth contact (1, relay R is again energized, this time through conductor 447, contacts of key a and contact II, and again locks itself and closes the actuating circuit of switch S through the iu terrupter I thereby causing the switch to continue stepping to its normal position. The attraction of armature 1 of It opens the series circuit oi relays It and R (Fig. 8), and the latter relay upon deiinergixation opens the circuit of clutch magnet M at r which brings the conue. .:tor switch S to rest with its wipers in engagement with the first set of contacts in the fourth tens group of the two-hundreds group. During the energization of 22 the locking circuit of R was opened at 1', and the de'tnergization of it connected grounded pole of battery to wire 5%. The dei nergization of R therefore completes the circuit of R, which circuit may be. traced as follows: batterythrough contacts 21()2 l6 of the Olf-IlOX'llltlb springs of S, .264, 5397, R. 59$), 7' 598 to ground through contact of it. Actuation of it shifts the connection of wires 580 and from 583 and to and 586, X'QSPQUiiYQl), connects wire 581 to wire 58:), rcmorcs the shunt from wires 585, 586 through 7, and completes the cir-- cuit of through a front contact. Circuit of R ,may be traced as follows: battery through off-normal springs 2l()2i(3. wire 264, 597, 595, R 594. contact of R to ground. Actuation of R opens the circuit through conductor 240 and locks itself to ground. Switch C now takes its fifth 'tep bringing its wipers into engagement with the fifth contacts of their respective rows which energizeslt through wire 450 and wiper "we" and connects ground through wiper '10s and its fifth contact to wire 600 leading to the third key strip K Relay R" is now connected in series with relay It and the resistancer as follows: B (Fig. 8). R, 444,

m", 585, front contact of R, 580, 9' 581, front contact of R 586, contact 7*, 16 into Fig. 7, and thence. from the tip control circuit of Figs. 7 and 9 as previously traced through I (Fig. 10), 404, 7' to ground. As one of the contacts 577 is already closed by the wipers of S the resistance 51' is shunted out of the series circuit of relays R" and it, giving the. maximum current flow which energizes both relays. R".'energizin causing the switch S to take one step, amin energizingcompletes thecircuit 'froin ground through of B 2215,

tion of M again starts-the switch. S to rotatingwhich in passing from. contact 577 momentarily removes the shu'ntfrom around 1' thus diminishing the current flow which while maintaining the energization of R causes R to retract its armature and deenergize M Upon closure of the next contact 577, R" is again energized this time the shunt circuit being from conductor 580 through contact 577 over conductor 581 through arm aturer of R to conductor 585, the second energization of R", starting S. around another step, and so on until wiper 18" engages contact d. R is now energized by current from ground through wiper cos, of'S through wire 600, contacts of key k and contact all, and upon actuation again locks itself and starts the switch S to restoring to its normal position. Actuation of R" also opens the series circuits R and R at r and R retracting its armatures opens the circuit of the clutch magnet M at 21}. It is to be noted here that upon the actuation of R, that It s again energized through armature r locking itself r of R and removingground from wire 598 to which ground was previously connected through a front contact of The .deenergization of ground from wire 598 which opens the circuit of B, which in turn opens the ener- 'gizing circuit of R, the latter relay, remaining locked through affront contact.

' Just before the switch S resumes its nor- .mal position the wiper s engaging contact d completes a circuit from ground through (PT 451 into Fig. 9, front contact of R,

sleeve conductor 132 and'thence over the sleeve control circuitthrough Fig. 7 into igi 8 and through windings of R to ground over the same path as previously traced for said relay. Theactuation of R this time, does not affect clutch magnet M as the circuit through conductor 240 is maintained open by the locked relay It. Attraction of armature r opens the locking circuit of It, and the attraction of r completes the test circuit so that'ifthe-called line is busy, battery potential existing'at its sleeve contact 578 willcause the energize,- tion of-test relay R by current over the fol lowing path: contact 578, sleeve conductor 18, 6' 252, 7' 251. R, 20.1; to ground 1 way of wire 200. it upon actuation locks itself to battery through r connects the busy back circuit l3 to the sleeve conductor 16.; and completes the circuit of release relaylt. armature Circuit oil? may be traced from 1*,267. 269, R to ground. It

up n actuati n l cks itself through r wire and ringing relay 601, 261, cit-normal sp.rings'246210 to battery'and completes the circuit of h to I Actuation of M causes the switch S-to continue to rotate until 1t reaches normal position as shown whereupon the oil-normal contacts 237'238are opened deenergizing M and allowing theswitch to come to rest in its normal position. The busy test potential at contact 578 may be traced to battery as follows: Upper member of 578 through the multiple of 57S engaged by the wiper of a previously connected switch, and thence through the circuits of said switch by way of sleeve conductor 18, 253, 1- 252, back contact of 1' 259, R 261, 250, r to battery.

After the test impulse relay R is deenergized, and completes the restoring circuit of switch 8 through: B, W, 250, T 261, 270, w, 271, a 212, 213, 1 214., 215, 1' 272, ws".",-s 274-, I to ground.

Magnet M is intermittently energized until switch S reaches normal position when it}; circuit is opened between ws and s The test relay it remains locked, holding busy-back l3 on trunk conductor 16, to signal the calling subscriber (Fig. 6), who then hangs up his receiver, opening circuit of R (Fig. 7 which energizes release relays R and R in a circuit from ground at oil-normal contact 568 through 567, 595, contact of R, 571, It and R in multiple to battery B. The switch S in restoring opens the circuit of B ,(Fig. 8) at the test contact 576 thus disconnecting the busy-back.

Immediately after the test impulse, the

switch-S arrives at its normal or zeroposition, and wiper s engaging contact (1, sends an impulse over wire 151, stepping switch S (Fig. 5) forward one step bringing its wipers onto'the sixth contact set.' When ws engages contact 68 the restoring relay R is energized through: B, 86, 11,0, 166, 68 to 98 ws 164. 1 to ground. Relay R opens circuit of It and R (Figs. 5. and respectively), at r and 1' While '7'? connects magnet M for intermittent encrgization through: '13", 86, 110, 117, M 153, 165, I to ground. Magnet M steps switch E5 forward, holding R energized through 108 and, contactsfis to 93", until. the wipers have reached normal position, as shown. The secondary selector switch S is restored by the cam on the switch S, in passing, and the operators circuit is ready to receive another call.

Assuming that the called subscriber is not busy R upon energization by the test impulse opens locking circuit of R which in turn partially closes the circuit of the R at p At the end of the test impulse R retracting its arinatures 

